Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH) , Pohang, Gyungbuk 790-784, Republic of Korea.
Department of Chemical and Biological Engineering, Sookmyung Women's University , 100 Cheongpa-ro 47-gil, Yongsan-gu, Seoul 04310, Republic of Korea.
ACS Nano. 2017 Jul 25;11(7):6586-6593. doi: 10.1021/acsnano.6b07617. Epub 2017 Jun 22.
Colloidal metal-halide perovskite quantum dots (QDs) with a dimension less than the exciton Bohr diameter D (quantum size regime) emerged as promising light emitters due to their spectrally narrow light, facile color tuning, and high photoluminescence quantum efficiency (PLQE). However, their size-sensitive emission wavelength and color purity and low electroluminescence efficiency are still challenging aspects. Here, we demonstrate highly efficient light-emitting diodes (LEDs) based on the colloidal perovskite nanocrystals (NCs) in a dimension > D (regime beyond quantum size) by using a multifunctional buffer hole injection layer (Buf-HIL). The perovskite NCs with a dimension greater than D show a size-irrespective high color purity and PLQE by managing the recombination of excitons occurring at surface traps and inside the NCs. The Buf-HIL composed of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) and perfluorinated ionomer induces uniform perovskite particle films with complete film coverage and prevents exciton quenching at the PEDOT:PSS/perovskite particle film interface. With these strategies, we achieved a very high PLQE (∼60.5%) in compact perovskite particle films without any complex post-treatments and multilayers and a high current efficiency of 15.5 cd/A in the LEDs of colloidal perovskite NCs, even in a simplified structure, which is the highest efficiency to date in green LEDs that use colloidal organic-inorganic metal-halide perovskite nanoparticles including perovskite QDs and NCs. These results can help to guide development of various light-emitting optoelectronic applications based on perovskite NCs.
胶体金属卤化物钙钛矿量子点（QD）的尺寸小于激子玻尔直径 D（量子尺寸范围），由于其光谱窄的光、易于颜色调谐和高光致发光量子效率（PLQE），因此成为有前途的发光体。然而，它们的发射波长和颜色纯度随尺寸敏感以及低电致发光效率仍然是具有挑战性的方面。在这里，我们通过使用多功能缓冲空穴注入层（Buf-HIL），展示了基于胶体钙钛矿纳米晶体（NCs）在尺寸>D（超越量子尺寸范围）的高效发光二极管（LED）。通过管理在表面陷阱和 NC 内部发生的激子复合，尺寸大于 D 的钙钛矿 NCs 表现出尺寸无关的高光纯度和 PLQE。由聚（3,4-亚乙基二氧噻吩）/聚（苯乙烯磺酸盐）（PEDOT：PSS）和全氟离子聚合物组成的 Buf-HIL 诱导具有完整膜覆盖的均匀钙钛矿颗粒膜，并防止在 PEDOT：PSS/钙钛矿颗粒膜界面处的激子猝灭。通过这些策略，我们在没有任何复杂后处理和多层结构的情况下，在致密钙钛矿颗粒膜中实现了非常高的 PLQE（约 60.5%），并且在胶体钙钛矿 NCs 的 LED 中实现了 15.5 cd/A 的高光电流效率，即使在简化的结构中，这也是使用胶体有机-无机金属卤化物钙钛矿纳米粒子（包括钙钛矿 QD 和 NC）的绿光 LED 中迄今为止的最高效率。这些结果可以帮助指导基于钙钛矿 NC 的各种发光光电应用的发展。
